It is known that a terminal of a core wire in an electrical wire is connected to a bus bar through ultrasonic welding. Specifically, an ultrasonic welding jig including an anvil and a welding horn is provided, and after a bus bar is placed on the anvil, the core wire of the electrical wire is placed on the bus bar. By applying ultrasonic vibration along the axial direction of the core wire while pressing the core wire using the welding horn, the core wire is ultrasonically welded to the bus bar (see Patent Document 1 below).